revlog: fix _cache usage in revision()

As documented at revlog.__init__, revlog._cache stores raw text.

The current read and write usage of "_cache" in revlog.revision lacks of
raw=True check.

This patch fixes that by adding check about raw, and storing rawtext
explicitly in _cache.

Note: it may slow down cache hit code path when raw=False and flags=0. That
performance issue will be fixed in a later patch.

test-revlog-raw now points us to a new problem.

mercurial/revlog.py

@@ -1267,7 +1267,9 b' class revlog(object):'
             return ""
         if self._cache:
             if self._cache[0] == node:
-                return self._cache[2]
+                # _cache only stores rawtext
+                if raw:
+                    return self._cache[2]
             cachedrev = self._cache[1]
 
         # look up what we need to read
@@ -1294,7 +1296,7 b' class revlog(object):'
         if validatehash:
             self.checkhash(text, node, rev=rev)
 
-        self._cache = (node, rev, text)
+        self._cache = (node, rev, rawtext)
         return text
 
     def hash(self, text, p1, p2):

tests/test-revlog-raw.py.out

@@ -1,1 +1,1 b''
-abort: rev 5: wrong text
+abort: crashed: integrity check failed on _testrevlog.i:11